1. Field of the Invention
The invention relates to a stabilized absorbent rayon web and more particularly to such a web demonstrating an improved resistance to surface abrasion, improved dimensional stability, and to structures made with such a web.
2. Description of the Prior Art
The stabilized absorbent rayon web of the present invention has many uses. It may be used alone or as outer plies for a wide variety of absorbent structures. While not intended to be limiting, an exemplary list of such structures may include washcloths, towels, bandages and dressings, surgical towels, surgical sponges and gauze-like structures. The stabilized rayon web of the present invention is particularly well suited for use as or in surgical structures because it is absorbent, soft, pliable, conformable and cloth-like, with excellent drape and hand. The stabilized rayon web maintains these desirable attributes even when wet. The outer or upper surface of the stabilized rayon web is non-abrasive and thus would not be abrasive to delicate tissues in the body when used as a surgical aid. Of great importance to the use of this material in surgical structures is the fact that the stabilized rayon web requires no additives such as bonding agents, surfactants (including wetting agents), surface finishes or the like. Any of these agents can cause concern from the aspect of safety when used in contact with delicate body tissues. The thermoplastic web used to stabilize the rayon web can readily be selected from thermoplastic materials generally recognized to be safe for surgical uses.
Prior art workers have devised a number of rayon or rayon-containing nonwoven webs or fabrics stabilized to maintain their integrity as a web.
Early examples were webs of all rayon staple length fibers or a blend of rayon and other staple length fibers, either air laid, wet laid or carded and bound together by saturating the web totally or intermittently with a bonding agent. The web was stabilized throughout its thickness and the bonding agent constituted an additive.
Another such stabilized web comprised a blend of staple length rayon fibers and thermoplastic staple length fibers. The thermoplastic fibers were uniformly distributed throughout the thickness of the web. The web was carded and heat embossed. While the embossing tended to stabilize the web, the thermoplastic penetrated throughout the web, rather than from the bottom surface of the web to a controlled depth therein. The embossing also resulted in an alteration and compaction of the web surface. Such a fabric is was for example, in U.S. Pat. No. 3,507,943, in the names of J. J. Such and A. R. Olson, issued Apr. 21, 1970.
U.S. Pat. No. 2,862,251, in the name of Frank Kalwaites, issued Dec. 2, 1958, taught a web of staple length rayon fibers, which was hydraulically needled and treated with an acrylic latex bonding agent for stabilization. Again, the web was stabilized throughout, its thickness, tending to detract from its surface aesthetics. This web also lacked wet bulk and resiliency.
Yet another prior art stabilized web was taught in U.S. Pat. No. 3,485,706, in the name of Franklin J. Evans, issued Dec. 23, 1969 and U.S. Pat. No. 3,486,168 in the names of Franklin J. Evans and Ronald J. Summers, issued Dec. 23, 1969. The web constituted an unbonded web of staple length rayon fiber which was hydraulically needled.
Prior art workers have produced rayon webs of carded or air laid staple length rayon fibers, which have been stitched in the machine direction by using continuous filament polyester thread. Such webs were not strongly resistant to surface abrasion and linting due to an abundance of free fiber ends. Additionally, these nonwovens raveled at the cut edges unless stitched, thus increasing the propensity to lint.
Spunbonded webs of rayon are available. Such webs demonstrate excellent drape and hand and are soft, pliable and conformable. By virtue of the fact that they are spunbonded and hence are continuous filament-type webs, the amount of available particulate material or lint that can fall off or be released from such webs during use is greatly reduced. This is true largely due to the absence of fiber ends which could break off when mechanical energy is applied to the surface of these webs. Such webs are, however, lacking in tensile strength and dimensional stability, particularly when wet. As used herein, the phrase "dimensional stability" relates to resistance to non-recoverable deformation by elongation or stretching. Such webs demonstrate poor wet bulk. As used herein, the phrase "wet bulk" relates to the resistance to the loss of form and resiliency when wet. The surface of these webs is not stable or resistant to abrasion, and although lint is not likely to be released, the surface fibers will become disentangled with mechanical working, reducing the usefulness of the material. This is due to relatively weak cross-over bonding at filament intersections.
Unlike prior art rayon webs, the stabilized absorbent rayon web of the present invention combines dimensional stability (both wet and dry) and enhanced tensile strength with excellent cloth-like surface characteristics and resistance to abrasion and linting. The teachings of the present invention enable spunbonded and staple length discontinuous fiber rayon webs, with their desirable aesthetics and functionality, to be used in end products where strength, surface abrasion resistance and dimensional stability requirements would normally preclude their use. This is especially true if the end product is to be used in the wet condition.